The thermoluminescence response of doped SiO2 optical fibres subjected to fast neutrons

This paper describes a preliminary study of the thermoluminescence (TL) response of doped SiO2 optical fibres subjected to 241AmBe neutron irradiation. The TL materials, which comprise Al- and Ge-doped silica fibres, were exposed in close contact with the 241AmBe source to obtain fast neutron interactions through use of measurements obtained with and without a Cd filter (the filter being made to entirely enclose the fibres). The neutron irradiations were performed for exposure times of 1-, 2-, 3-, 5- and 7-days in a neutron tank filled with water. In this study, use was also made of the Monte Carlo N-particle (MCNPTM) code version 5 (V5) to simulate the neutron irradiations experiment. It was found that the commercially available Ge-doped and Al-doped optical fibres show a linear dose response subjected to fast neutrons from 241AmBe source up to seven days of irradiations. The simulation performed using MCNP5 also exhibits a similar pattern, albeit differing in sensitivity. The TL response of Ge-doped fibre is markedly greater than that of the Al-doped fibre, the total absorption cross section for Ge in both the fast and thermal neutrons region being some ten times greater than that of Al

Perovskites as surface-assisted room temperature protonic conductor humidity sensor

This paper shows a correlation between surface effective porosity due to various sintering regimes and humidity sensitive electrical properties of the perovskite-based bulk type humidity sensors. Furthermore, room temperature humidity transduction mechanism of the thick film type humidity sensors was studied in details through electrochemical impedance spectroscopy (EIS) and major transmissive components were detected by fitting to the equivalent circuits. The materials were synthesized employing solid state reaction and bulk and film type devices were fabricated by hydraulic pressing and screen printing techniques, respectively. The morphological and elemental characterizations were carried on using FESEM, EFTEM, and EDX. Physical properties including open porosity/bulk density were investigated through ASTM methods. An innovative self-designed material test fixture with ceramic supports was fabricated for high S/N ratio electrical measurement of the bulk samples. All the sensors were set up at 20-95% RH. The morphological, physical, and electrical results of bulk pellets indicate direct correlation of the open cavities and AC conduction. Presence of the ionic transport is clearly observed from the frequency-conductance spectra at room temperature. Noise-free detected behavior via EIS proves that proton transfer mechanism is a dominant responsible

Silver influence of physical and thermo luminescence properties on lithium-Strontium-borate LSBO: Ag exposed to cobalt-60 gamma ray

This work investigates the properties of glow curve of lithium Strontium borate doped sliver glass (LSBO: Ag), subjected to Co-60 gamma irradiation. The glass samples were prepared in different compositions based on 15%Li2CO3+2%SrCO3 (83-x) H3BO3 +xAgNO3, where x = 0.001, 0.003, 0.005, 0.007, 0.009 and 0.01 mol% by traditional melting quenching method at temperature 1300 °C for 1 hour. The structural pattern of glass samples has been identified by X-ray diffraction. The XRD pattern shows that the samples are glasses since there is broader peak appearing in the spectral pattern. FESEM images verify the homogeneous and transmitting surface morphology of all samples. Stable glasses with Hurby parameter ~ 0.5 are achieved. EDX spectra determine the accurate elemental compositions in the samples. Physical properties are determined in terms of glass density, molar volume, polar on radius, inter-nuclear distance, and ion concentration. Glass density is found to increase from 2.45 to 2.46 g cm-1 after addition of AgNO3 concentration. The TL intensity at different compositions of lithium borate doped sliver glass after exposed to 50 Gy Co-60 gamma-rays is presented. The results clearly show that the highest TL intensity is found in glass composition of 0.09 mol% of AgNO3

Evaluation of three RNA extraction methods from three cultivars of Malaysian upland rice

Rice (Oryza sativa L.) can be divided into two major categories, which is upland rice and lowland rice. Apart from being the staple food for more than half of the world population, it is also known as model plant for functional genomics study. However, it possess high amount of starch and polysaccharide that makes the isolation of good quality RNA for downstream purposes often a difficult task. While there are many studies being carried out for lowland rice extraction, none has been reported for upland rice. This study is the first to report on evaluation of three RNA extraction methods for three Malaysian upland rice cultivars in order to determine the best method to isolate high grade RNA. The result obtained demonstrated that good quality RNA in terms of integrity, purity and quality can be isolated from young leaves of these cultivars by using guanidine isothiocyanate based extraction method that is fast, simple and efficient and had been proven suitable for further downstream applications

Efficient Callus Induction and Regeneration in Selected Indica Rice

An efficient callus induction and in vitro regeneration were developed using plant growth regulators, carbon sources, and basal media for three selected Malaysian wetland rice varieties (MR220, MR220-CL2, and MR232) and one upland variety (Bario). Effect of plant growth regulator (PGR) was carried out using four different concentrations (1–4 mg/L) of 2,4-D (2, 4-dichlorophenoxyacetic acid), and NAA (1-naphthalene acetic acid) (2.5, 5.0, 7.5, and 10 mg/L) with optimized 2,4-D. Effects of carbon sources (maltose and sorbitol), and basal media (MS, N6, and LS) were also studied with optimized PGR to maximize the induction of regenerable calli. This study found that all four varieties exhibited high frequency of callus induction on MS (Murashige and Skoog) medium that was supplemented with 3 mg/L 2,4-D and 30 g/L maltose. Callus induction frequencies in the cases of MR220, MR220-CL2, MR232, and Bario were found to be 76%, 94%, 85%, and 42% respectively. Morphological analysis through scanning electron microscopy (SEM) and histological analysis revealed the embryogenicity of the induced callus. In the regeneration study, it was observed that combination of 2 mg/L BAP (6-benzylaminopurine), 2 mg/L Kin (Kinetin) and 0.5 mg/L NAA supplemented MS medium has the potential to promote regeneration of selected indica rice varieties with higher regeneration percentage, i.e., 82% (MR220-CL2), 68% (both in MR220 and MR232), and 40% (Bario). The optimized conditions for callus formation and regeneration can be useful for biotechnological practices for the genetic improvement of Malaysian indica rice

Investigation of room temperature protonic conduction of perovskite humidity sensors

This paper shows a correlation between surface effective porosity due to various sintering regimes and humidity sensitive electrical properties of the perovskite-based bulk type humidity sensors, at room temperature. Furthermore, room temperature humidity transduction mechanism of the thick film type humidity sensors was studied in detail through electrochemical impedance spectroscopy (EIS) and major transmissive components were detected by the fitting of the Bode diagrams and Nyquist complexes to the equivalent circuits. The microstructural, morphological and elemental characterizations were carried on using XRD, EFTEM, FESEM, and EDX. Physical properties including open porosity/bulk density were investigated through American Standard Test Method (ASTM). An innovative self-designed material test fixture with ceramic supports was fabricated for a high S/N ratio electrical measurement of the bulk samples. All the sensors were set up at 20-95% RH. The morphological, physical, and electrical results of the bulk pellets indicate a direct correlation of the open cavities and AC conduction. The higher the open porosity is, the greater is the conduction and vice versa. Presence of the ionic transport is clearly observed from the frequency-conductance spectra at room temperature. Noise-free detected behavior via EIS proves that the proton transfer mechanism is a dominant responsible, and executed by both charge transfer resistance and kinetically controlled charge transfer (diffusive species) at low and middle to high RH. Next to the Warburg effect (at 80% RH), for the first time, a Gerischer impedance was found as a dominant agent of transduction at 85% RH to above

Optimization of thermoluminescence response of copper doped zinc lithium borate glass co-doped with Na2O

Establishing the basic procedures that will influence the enhancement of the TL yield of a phosphor is paramount in the issue of dosimetry. Melt quenching method was adopted in synthesizing lithium borate glass modified with ZnO, doped with CuO and codoped with Na2O. The structural and optical properties of zinc lithium borate and some TL properties of copper doped zinc lithium borate were reported in our previous works. The amorphous nature of the prepared glasses was confirmed by x-ray diffraction analysis (XRD). Physical properties of the glass were obtained via Archimedes principle. The copper doped zinc lithium borate was co-doped with different concentration of Na2O (0.025 mol % to 0.1 mol %). The glasses were irradiated with 4 Gy dose of gamma rays using 60Co gamma cell. The highest TL response was recorded against 0.05 mol% concentration of Na2O. The best settings for TLD reading of the proposed TLD were determined. The optimal annealing temperature and time for this composition was found to be 300 oC and 50 min respectively. The best heating rate at which the new TLD can be readout was 3 oC S-1

Barium strontium titanate humidity sensor: impact of doping on the structural and electrical properties

The influence of Mg2+ doping (3 mol %) on structural and humidity sensing properties of (Ba0.5,Sr0.5)TiO3 (BST) perovskite nanocomposite were studied in details. Microstructural properties revealed the particle size, surface area, and average pore volume diminished for doped sample. For the MgO doped BST sensor, the film resistance and total impedance are changed more than four orders of magnitude in the 20–95% RH range, while BST sensor shows three orders change. The 3 mol % MgO doped sample with maximum hysteresis of 6.1 RH% and response/recovery time of about 30/80 s exhibits faster characteristics compare to pure BST sample with 6.8 RH% hysteresis and response/recovery of 41 s and 98 s, respectively. Transduction mechanism was found based on the proton transfer and further confirmed by a Bode plot and Nyquist complex impedance plane plot

ASSESSMENT OF DOSE INTAKE OF TOXIC ELEMENTS IN GROUNDWATER SAMPLES FROM ABUJA, NORTH CENTRAL NIGERIA

This study measured the concentrations of toxic carcinogenic and non-carcinogenic elements present in groundwater using Inductively Coupled-Plasma Mass Spectrometry (ICP-MS). The concentration values obtained were used to calculate the life average daily dose (LADD) exposure of the people whom rely on groundwater for consumption in Abuja, Nigeria. The highest LADD for the carcinogenic toxic element chromium (Cr) was 2.7 x 10-5 μg kg‒1 day‒1, whereas it was 3.3 x 10-4 μg kg‒1 day‒1 for the non-carcinogenic toxic element lead (Pb), identified in water samples collected by the Water Board. These LADD magnitudes of 10-5 and 10-4 for both carcinogenic and noncarcinogenic toxic elements in groundwater are far below the International Reference Dose according to the United States Environmental Protection Agency (USEPA) in 2008, which has a value of 10-1. The low magnitudes found in water samples may not pose significant health risks to the local population. The relevant authorities should, therefore, continue to monitor the impact of human activities on metal pollution in this area and take effective measures to control contamination of the public water suppl

Thermoluminescence response of nanoparticles gold doped lithium borate glass subjected to photon irradiation

The absorption coefficient of Borates glass is much closed to human body tissue. This fact makes borates as an ideal material for thermoluminescence material either for medical or environmental application. In this study, a glass system of 15% Li2CO3+ 85% H3BO3 doped with 0.1mol %nano-gold was prepared by using melt-quenching technique. Undoped and Au doped lithium borate glass samples were exposed to Co-60 gamma ray (1.25 MeV) with various doses ranging from 10 to 60 Gy by using Gammacell 220 excel. Various TL properties such as TL glow curve, linearity and sensitivity of the prepared glass were investigated. From the TL glow curve, it was found that the TL intensity increased by addition of Au into the glass system. The TL intensity of Au doped glass increases about 23 times higher than the undoped glass. The study also shows that the doped borate glass has a linear response subjected to Co-60 gamma irradiation at doses ranging from 10 to 60 Gy. The sensitivity of doped glass is about 22 times higher compared to un-doped glass